1. Technical Field
This disclosure relates to radiographic imaging, and more particularly, to a method for detecting anatomic landmarks in radiographic images, preferably for Total Hip Replacement (THR) applications.
2. Description of the Related Art
In Total Hip Replacement surgery, a prosthesis to be implanted in a patient should be chosen based on the size of the patient""s anatomy. Typically, an X-ray image is first taken of the patient. Then, some specific landmarks on the radiograph are manually selected and measurements are made to find the most appropriate prosthesis from a database. This is referred to presently as pre-surgery planning. To determine whether a THR has been successful, regular follow-ups extending as long as 12 years need to be made. During these follow up visits, a set of landmarks need to selected from the radiographs, and measurements are made to determine the relative position changes of prosthetic components with respect to other bones over time.
The most common long-term problem following a THR is loosening. Wearing may also occur. Due to the large number of radiographs that need to be reviewed, the work overload for physicians is enormous. The most time-consuming part is the manual landmark selection. Depending on physician""s experience and expert knowledge, this is also subject to inter-person and intra-person errors.
Therefore, a need exists for a fully automatic computer method for landmark detection and measurement for total hip replacement.
A method for automatically detecting anatomical landmarks in a radiographic image, in accordance with the present invention, provides a region of interest of the image, and determines a first landmark in the region of interest by computing an intensity ridge map. A second landmark is determined in the region of interest based on a position and orientation of the first landmark, and measurements are performed on the image based on positions of the first and second landmarks.
In other methods, the first landmark may include a femur, and the second landmark may include an outer boundary of the femur. The second landmark may alternately include a femoral head. The method may include the step of determining a next landmark in the region of interest based on a position and orientation of a previously determined landmark. The step of performing measurements may include the step of selecting a prosthesis based on a plurality of determined landmarks. The step of performing measurements may include the step of determining movement and wear of a prosthesis based on a plurality of determined landmarks. The first landmark may include a feature of a prosthetic femur, and the second landmark may include a portion of a pelvis.
A method for automatically detecting anatomical landmarks in a radiographic image of a hip, includes the steps of providing a radiographic image of a pelvis region, generating an intensity ridge map to highlight ridges in one direction, determining a position of a leg in the image by employing a strongest ridge in the ridge map to approximate the leg orientation and position, determining inner contour lines of a femur of the leg in the image based on a position and orientation of the strongest vertical ridge, determining outer surface lines of the femur based on a position and orientation of the inner contour lines and the ridge map, determining points of maximum curvature on a femoral head of the femur and tracing the femoral head by employing the ridge map, determining a center of the femoral head and selecting a prosthesis based on the inner contour lines, the points of maximum curvature and the center of the femoral head.
In other methods, the step of performing measurements on the image based on positions of determined landmarks may be included.
A method for automatically detecting anatomical landmarks in a radiographic image of a hip having a prosthesis, includes the steps of providing a radiographic image of a pelvis region, generating an intensity ridge map to highlight ridges in one direction, determining a position of a leg in the image by employing a strongest ridge in the ridge map to approximate the leg orientation and position, determining a boundary of the prosthesis in a femur of the leg in the image based on a position and orientation of the strongest ridge, determining a position of a femoral component head of the prosthesis by testing the boundary of the prosthesis in accordance with an expected shape, tracing an arcuate line of ilium by employing the position of the femoral component head and performing measurements to determine a degree of wear and loosening of the prosthesis.
In other methods, the step of tracing a boundary of an obturator foramen to find centers of the obturator foramen may be included. The method may include the step of determining a public symphsis based on the centers of the obturator foramen and the arcuate line of ilium.
The above methods may be implemented in a program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform these method steps.